Affiliation:
1. Department of 3D Printing Materials Korea Institute of Materials Science (KIMS) Changwon Republic of Korea
2. Department of Materials Science and Engineering Pusan National University Busan Republic of Korea
3. Department of Advanced Materials Engineering University of Science & Technology (UST) Daejeon Republic of Korea
Abstract
AbstractGeopolymer ceramics undergo a series of thermal phase transitions, progressing from an amorphous geopolymer gel to a crystalline phase, and eventually to an amorphous glass phase as the temperature increases. However, there is a lack of mechanism understanding regarding to the crystallization process and the subsequent thermal degradation. Here, we fundamentally investigated the kinetics of nepheline formation in Na‐based geopolymer systems and its thermal stability up to 1400°C. Nepheline crystallization is controlled by bulk nucleation and three‐dimensional crystal growth based on the Avrami factor of 4.64, where the activation energy of nepheline formation is 350.59 kJ/mol. High thermal stability of geopolymer ceramics is achieved due to the appearance of nepheline up to 1400°C with the Si/Al ratio ranging from 1.40 to 1.94, while melting and amorphous structure are formed above a higher Si/Al ratio of 2.22. The nature of sintering for geopolymer ceramics consists of shrinkage, expansion and shrinkage corresponding to dehydroxylation, crystallization, and densification, leading to a thermal shrinkage of 21% at 1400°C.
Subject
Materials Chemistry,Marketing,Condensed Matter Physics,Ceramics and Composites